Transposon

Image courtesy of Lauren Solomon, Broad Communications

A transposon (or transposable element) is a small piece of DNA that inserts itself into another place in the genome. Geneticist Barbara McClintock discovered these genetic elements while studying corn in the 1940s. McClintock noticed that spontaneous breaks in the plant’s chromosomes correlated with the color patterns of the corn. She later revealed that certain bits of DNA — she called them “jumping genes” — have the ability to move within and between chromosomes, causing the breaks she saw.

How these jumping genes get around can vary. For example, some make copies of themselves first, and then these copies insert into another position of the genome. Others move directly to another position by a “cut and paste” mechanism.

Transposons have since been identified in a variety of organisms, ranging from bacteria to humans. In the process of inserting into the genome, transposons can interrupt the normal spelling of DNA, creating gene mutations with a variety of effects. They may turn nearby genes off, preventing their ability to create protein, or they may turn them on, increasing the amount of protein made.

There is evidence that transposons aren’t just “selfish genes” intent on replicating themselves or genomic “junk” that provides no benefit to the host. They may play a creative role in building new functional parts of the genome (see this story on the Broad Institute’s research). Recent research has shown that transposons may help plants respond and adapt to environmental stress by regulating other genes. In bacteria, transposons often carry genes that impart resistance to antibiotic substances, helping the bacteria survive.

Want to learn more?

Interested in Barbara McClintock’s groundbreaking work on jumping genes? Learn more at the Nobel Prize website.

You can view this McGraw-Hill animation to find out how transposons can insert themselves into the genome.

Read the Broad Institute news story on the sequencing of the opossum genome, and the discoveries revealed about the role of jumping genes in evolution.